Mechanical Operations

281. Sphericity of pulverised coal is

  1. 1
  2. < 1
  3. > 1
  4. ∞

Correct answer: (B)
< 1

282. Sphericity of raschig ring (whose length and diameter are equal) is

  1. > 1
  2. < 1
  3. 1
  4. 2

Correct answer: (C)
1

283. Stamp mills are generally used for crushing

  1. Iron ores
  2. Gold ores
  3. Talc
  4. Diamond

Correct answer: (B)
Gold ores

284. Sulphuric acid mist is arrested by using a _________ scrubber.

  1. Packed wet
  2. Hollow wet
  3. Venturi
  4. Co-current

Correct answer: (C)
Venturi

285. Supporting legs of a plate and frame filter is normally made of

  1. Stainless steel
  2. Cast iron
  3. High speed steel
  4. Wooden plank

Correct answer: (B)
Cast iron

286. Tabling process used for separating two materials of different densities by passing the dilute pulp over a table/deck, which is inclined from the horizontal surface at an angle of about

  1. 1 to 2°
  2. 2 to 5°
  3. 5 to 10°
  4. 10 to 15°

Correct answer: (B)
2 to 5°

287. Tabular bowl centrifuges as compared to disk bowl centrifuges

  1. Operate at higher speed
  2. Employ bowl of larger diameter
  3. Can't be operated under pressure/vacuum
  4. Can't be used for separation of fine suspended solids from a liquid

Correct answer: (A)
Operate at higher speed

288. Tank filter (e.g., Nutsche filter) is

  1. A high pressure filter
  2. A continuous filter
  3. Used for small scale filtration work
  4. A leaf filter

Correct answer: (C)
Used for small scale filtration work

289. Temperature of the product during ultrafine grinding

  1. Increases
  2. Decreases
  3. Remain constant
  4. May increase or decrease; depends on the material being ground

Correct answer: (A)
Increases

290. The basic filtration equation is given as dt/dV = (μ/A ΔP). [(α .CV/A) + Rm], where, V is volume of the filtrate; A is the filtration area, a is specific cake resistance, μ is viscosity of the filtrate, and C is the concentration of the solids in the feed slurry. In a 20 minutes constant rate filtration, 5 m3 of filtrate was obtained. If this is followed by a constant pressure filtration, how much more time in minutes, it will take for another 5 m3 of filtrate to be produced? Neglect filter medium resistance, Rm; assume incompressible cake.

  1. 10
  2. 20
  3. 25
  4. 30

Correct answer: (B)
20

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